Method of making deoxidized copper



Patented June 4, 1935 UNITED STATES PATENT OFFICE METHOD OF MAKING DEOXIDIZED COPPER No Drawing. Application September 9, 1933, Serial No. 688,826

10 Claims.

This invention relates to the manufacture and treatment of copper to be used in various forms such as bars, electrical conductor wires and so forth,- and has for an object to provide an improved method of deoxidizing the copper whereby a uniform product may be produced commercially and one having definite characteristics which may be secured with certainty and in an indefinite number of copper charges.

Another object is to provide such a method which may be accurately and repeatedly performed by the men of ordinary skill in the works to tsecure the desired results and a uniform produc A further object is to provide a method of deoxidizing copper whereby a conductor of high electrical conductivity and one which is able to withstand repeated bending without breaking after being annealed in hydrogen may be secured by the usual mill operatives and in an indefinite number of successive charges.

With the foregoing and other objects in view which will be apparent as the description proceeds, we have developed the method of deoxidizing copper as hereinafter set forth. it being understood that we are notnecessarily limited to the exact details disclosed but that variations may ltoe employed within the principles of the inven- It has been very difficult in mill operations to secure a uniform product in deoxidizing copper, and it has also been difiicult to produce dcoxidized copper with a high electrical conductivity and which will stand the desired amount of bending without breaking after annealing in hydrogen. We have discovered a method of deoxidizing copper by which we can produce the metal on a commercial scale with the usual operatives in the mill and with a uniformity which will maintain the desired standard-s. By this method we can, if desired, secure an electrical conductivity of at least 99.5 percent at 20 C. in terms of the International Annealed Copper Standard, and it can also withstand a minimum of ten bends after a thirty minute anneal in a hydrogen atmosphere at C. In this bending test the copper is bent around a radius 2.5 times the thickness or diameter of the copper rod, wire, or whatever the shape may be, the copper being first bent 90 in one direction and then back to the original position. This constitutes one bend. The second is in the opposite direction around the same radius 90 and then back to the original position. The third bend i; the same as the first and so on.

In our copending application, Serial Number 616,096, filed June 8, 1932, we have disclosed a method whereby copper capable of meeting the above tests can be uniformly produced on a commercial scale. That method involved the bringing of the molten copper to a definite end point after exposure to the air until it showed a boiling action, by stirring partially burned or calcined charcoal into the boiling metal until it became quiet, and then adding the required amount of metal deoxidizer to deoxidize the copper.

Metals have been used for many years to deoxidize copper but never before our present meth ods has such copper produced on a commercial scale passed the above tests, or been made in successive batches or charges on a commercial scale having uniform characteristics. In order for the copper to be uniform the amount of deoxidizer remaining in the finished copper must be kept uniform. Also in order for the copper to pass the above tests for electrical conductivity and resistance to bending there must be only minute amounts of the deoxidizer remaining in the finished copper, as only small amounts will materially reduce the electrical conductivity of the copper. On the other hand if there is not added a sufficient amount of the deoxidizer to completely deoxidize the copper then the copper is liable to swell on freezing in a mold and it cannot withstand the bending test above noted.

It will be evident that as it is difiicult to determine under ordinary operations the exact amount of the oxygen in the copper and therefore todetermine the exact amount of deoxidizer required to completely deoxidize the copper and still not have an objectionable surplus of the deoxidizer to remain in the copper and reduce the electrical conductivity, it was practically impossible to produce deoxidized copper commercially which was uniform orhad uniform characteristics, or which could meet the above standards.

We have discovered that with certain treatments of copper we can bring it to a definite end point or condition where it has a definite oxygen content and we therefore can determine the exthe deoxidizers if we so desire.

at 20 C. in the terms of the International Annealed Standard.

I In carrying out our method the copper may first be melted in any suitable furnace but we prefer theelectric furnace known in the trade as the induction furnace as the operations can more easily be controlled. However, we are not limited to the use of such furnace but may use other types of furnaces for melting the. copper, such for example as what is known in the trade as the high frequency furnace. Thelatter or high frequency furnace is preferred forvthe use in carrying out our method disclosed in our copending application above mentioned where an end point is used which is indicated by the metal becoming quiet as the result of stirring in charcoal after boiling when exposed to air.

In our present method the copper is preferably melted under reducing conditions,- preferably under a cover of charcoal but other covers may be used. We prefer the charcoal as this gives us less work and more definite control in another part of the method. When the copper is melted and a suitable temperature attained, preferably a temperature suitable for pouring, which is in the neighborhood of 1200 C., the charcoal or other cover is removed. The copper at this point contains gas, and if oxygen is present it is only inminute amounts. The copper may be melted without the cover but in this case after melting it should be subjected to reducing conditions until it is substantially deoxidized. After the charcoal is removed we may place electric current on the furnace and stir with a graphite rod and expose the copper to the air in this way. This stirring action while exposed to the air removes most of the gas from the copper although it is not necessary to remove all of it. As the copper was melted under the reducing conditions, although it may contain gases the oxygen content, if any, is very small. It will therefore be evident that if we expose the copper to the air after removing the charcoal cover for a given definite time this exposure and stirring action removes gas from the copper, probably most of the gas in the copper, and the copper is brought to a definite oxygen content or end point by partial oxidation of the copper, and if successive charges of approximately the same weight of cop- -per are exposed for the same length of time they will be brought to this same end point or condition. During this time the copper may or may not be stirred continuously and the current may or may not be on the furnace all of the time. At the end of this definite period of time, as described, the old and partly burned charcoal used as a cover in melting the copper down, or other carbon in a forin having a similar composition to partly burned or calcined charcoal, is placed on this second definite stirring period the copper has a definite oxygen content and the amount of deoxidizer required to completely deoxidize the copper or to produce a finished metal having given characteristics can readily be determined. If

copperof high electrical conductivity is desired At the end of only sufiicient of the metailic'oeoxidizer 15 added to completely deoxidize the copper and leave a minimum of the deoxidizer in the copper. While if high electrical conductivity, is not required somewhat more of the deoxidizer may be used as a surplus of the deoxidizer in'the finished copper might not be objectionable depending on for what purpose the metal is to be used. The end point at the end of the definite stirring time with charcoal gives us a definite condition from which the exactamount of deoxidizer required depending on the characteristics desired in the finished copper can be definitely determined, although it is not necessary to know what the oxygen content is at this point.

The exact amount of deoxidizer to be added after this end point is reached or at the end of this de 'te period is determined by testing. If after ad some deoxidizer it is insufiicient in "amount a bar cast from this metal will swell on freezing and will be unsound. If too much de-' oxidizer is added for the high electrical'conductivity this conductivity would be below 99.5 percent. Therefore upon observing the behavior of the metal on freezing and making the conductivity test the amount of deoxidizer required can be readily determined. These tests can be made for each deoxidizer it is desired to use and after once determined for each deoxidizer and for-the two definite periods of exposure to the air and stirring in of the charcoal, can be depended upon to give uniform results if the same conditions are observed in treating subsequent charges of cop per. We find that this end point is very definite for given conditions, and by introducing definite amounts of deoxidizer after the end point is reached for these conditions our finished metal invariably has the same characteristics.

The deoxidizer, such for example as metallic aluminum, may be added either as a metallic aluminum in small pieces or in order to secure very fine control of the aluminum content it may be added in the form of a-copper-aluminum alloy. Such alloy may contain 75 percent copper and 25 percent aluminum, or any other known propor- I tions may be used without affecting the principle of operation. It is also possible to use other metals than aluminum as the deoxidizer, such for example as lithium. or manganese or any other metallic or other suitable deoxidizers, such for example as silicon or calcium boride, or we may use combinations of two or more different deoxidizers. Thus for example we may partially deoxidize the copper with the aluminum and then complete the deoxidation by the addition of another metal such as manganese, preferably in the form of any alloy-of approximately 70 percent copper and 30 percent manganese to obtain a more delicate regulation or adjustment 'of the manganese content in the copper, but pure metal such as pure manganese may be added if preferred, or, of course, an alloy of different proportions of copper and the metal such as manganese. The molten deoxidized copper is then poured from under the charcoal cover into molds dressed with a suitable dressing. A heavy dressing of lard oil mixed with graphite has proven very satisfactory. As indicated above those familiar with the art will appreciate that covers other than charcoal may be used and also mold dressings other than lard oil and graphite may be used.

As a definite example of this method and operation 645 pounds of N. E. C. ingot copper (comprising approximately 99.9% pure copper) were melted under a heavy layer of charcoal in an electric induction furnace. Charcoal was used very freely as the copper was melted down, no attempt being made to use the charcoal sparingly. This melting operation usually requires about one hour and twenty-five minutes, although of course, variations of this time are to be expected.

When the copper was melted and the proper heat attained, which we estimate to be in the neighborhood of 1200 C. the charcoal was completely skimmed off. After skimming the charcoal the current was applied and during this time the copper may be stirred with a graphite rod. The application of the current agitates the copper considerably which is also assisted bystirringwith the graphite rod, and in the absence of the cover probably most of the contained gases are driven off or removed, and as the copper is exposed to the air some oxidation of the copper takes place. In the present example this exposure to the air was for a definite period, in the present case three minutes (although this time may be varied as will later be indicated). During this time the copper may or may not be stirred continuously and the current may or may not be on the furnace all of the time. This exposure to the air will oxidize the copper to a degree to give an oxygen content greater than the minute amounts which may already be in the copper. After exposure for the above noted length of time the oxygen content was less than 0.025 percent.

At the end of this three minute period the partially burned charcoal used in melting the copper down was again placed on the copper and this charcoal was stirred into the metal for a definite period, in the present example for two minutes. No attempt was made to weigh or use a predetermined amount of carbon in the form of partially burned charcoal. We merely shoveled partially burned charcoal back onto the copper regardless of the amount of charcoal skimmed off before the stirring of the copper in contact with air. The electric current may be on the furnace for all or part of this last stirring period as desired. This brings the metal to a definite end point or oxygen content, and at the end of this.

last stirring period we added the metallic deoxidizer. We may use one metal for deoxidizing the copper such as aluminum, manganese, calcium or other deoxidizers, or we may use two or more deoxidizers, preferably metallic if desired. The deoxidizers such as aluminum may be added to the copper in small pieces one at a time and each stirred in. The current is then placed on the furnace for a short time. Then the copperaluminum alloy may be added in the same manner. This alloy may also be in small pieces and is stirred in carefully, and it will be evident this gives a very fine control of the amount of aluminum. Current may then again be placed on the furnace for a short time. If the copper is not completely deoxidized at this point sufiicient aluminum may be added to do this, but we have found that the copper is improved in certain respects if we complete the deoxidation by the addition of manganese. For example the manganese makes the shear cut when the bars are gated much less drossy and clears up the metal very nicely. We may therefore add the alloy of copper and manganese at this point, this alloy preferably of approximately '70 percent copper and 30 percent manganese. This alloy is also added in small pieces one at a time which are stirred in and the current applied for a short time. This completes the deoxidation of the copper and the charge may then be poured into suitable molds. We have made large quantities of deoxidized copper by the method disclosed and secure very consistent and excellent results, the copper meeting the various requirements as outlined. Furthermore, this is a method of treating copper which can readily be performed by the men ordinarily employed in the works to secure the uniform results.

In the specific example above described we found that after stirring the copper in the presence of air our oxygen content was less than 0.025 percent and that after the period of stirring the charcoal into the copper the oxygen content was less than 0.010 percent. In other words when the metallic deoxidizer was added there was less than 0.010 percent oxygen present in the copper. It will be evident that these amounts of oxygen in the copper at the ends of the periods of the exposure to air and the stirring in of charcoal will vary depending on the length of time of the periods, which may vary considerably as we are not limited to the three and two minute periods given in the specific example described. It is preferred that the maximum content of oxygen be not over approximately 0.05 percent and probably would never go over 0.09 percent. Ordinarily it is not over 0.03 percent. Thus the lengths of these periods may be varied without affecting the final results, and for example, we might stir the copper five, six or ten minutes when the copper is exposed to the air and .then stir with charcoal for a given suitable length of time, which in this case would preferably be more than the two minutes mentioned. We wish to point out our method involves the stirring of the copper when exposed to the air for a definite length of time and then stirring in the presence of the charcoal for a definite length of time, all before adding the metallic deoxidizer. By following this method a definite oxygen content is obtained and a metallic deoxidizer can be controlled very nicely. Thus if it is determined that with stirring for a given definite time in contact with air and stirring in contact with charcoal for a given definite time prior to adding the given amount of deoxidizer secures the desired result, if successive charges of copper are stirred for the same lengths of time in contact with air and in contact with charcoal and the same amount of deoxidizer added, metal will be produced having the same characteristics as the first charge. In making deoxidized copper of the high electrical conductivity above mentioned we prefer to start with copper of a purity of 99.9 percent or better, but if it is not required to get high electrical conductivity it is not required that we use high purity copper.

Thus with the above method we have found we can produce in commercial quantities deoxidized copper of uniform characteristics and may also produce copper which will withstand the above noted tests for'electrical conductivity and bending, and we can definitely produce deoxidized copper having these characteristics and repeat as often as desired. This is possible because by this method before adding the deoxidizer the melted copper is brought to a definite point having a definite condition, or that is definite oxygen content, and this condition is the same for separate charges of copper if the same time periods of stirring while exposed to the air and stirring in the presence of charcoal are observed. This gives a definite condition from which the amount of deoxidizer required can be definitely determined. The copper can be rolled, drawn and otherwise worked into the desired shapes and forms for use, such as wires, rods, bars, etc.

Having thus set forth the nature of our invention, what we claim is:

1.' A method of making deoxidized copper comprising melting a plurality of succeeding charges of copper of approximatelv the same weight and composition under reducing conditions, exposing the succeeding melts to oxidizing conditions for the same definite period of time to permit escape of gases, stirring carbonaceous material similar in composition to partly burned or calcined char coal into the copper and for the same definite period of time for each melt, and adding to each melt deoxidizer which does not form a reaction product which is gaseous at room temperature upon combining with the oxygen of the copper and sufiicient in amount to deoxidize the copper.

2. A method of making deoxidized copper comprising melting a plurality of succeeding charges of copper of approximately the same weight and composition under charcoal, removing the charcoal and exposing the succeeding melts to the air for the same definite period of time and agitating them to permit escape of gases, stirring partly burned or calcined charcoal into the copper and for the same definite period of time for each melt, and adding to each melt sufiicient metallic deoxidizer to prevent swelling of the metal on freezing.

3. A method of making deoxidized copper comprising melting a plurality of succeeding charges of copper of approximately the same weight and composition under reducing conditions, exposing the succeeding melts to the air and agitating tor the samedefinite periods of time to permit escape of gases, stirring partly burned or calcined charcoal into the copper and for the same definite period of time for each melt, and adding to each melt sufiicient metallic deoxidizer to deoxidize the copp r.

4. A method of making deoxidized copper comprising melting a plurality of succeeding charges of copper of a purity of approximately 99.9%-0r over under charcoal, removing the charcoal and stirring the succeeding melts while exposed to the air for the same definite period of time to permit escape of gases, stirring partly burned or calcined charcoal into the copper and for the same definite period of time for each melt, and adding to each melt sufiicient metallic deoxidizer to deoxidize the copper.

5. A method of making deoxidized copper comprising heating a plurality of succeeding charges of copper of approximately the same weight and composition under charcoal to a temperature suitable for pouring, removing the charcoal and stirring the succeeding melts with a graphite rod while exposed to the air for the same definite period of time to permit escapeoi gases, placing 'partly burned or calcined charcoal on the melted copper and stirring it in for the same definite period of time for each melt, and adding to each melt suflicient metallic'deoxidizer to deoxidize the copper.

6. A method of making deoxidizcd copper comprising melting a plurality of succeeding charges of copper of approximately the same weight and composition under reducing conditions, exposing the succeeding melts to the air and stirring for the same definite period of time to permit escape of gases, stirring partially burned or calcined charcoal into the copper and for the same definite period of time for each melt, and adding to each melt noncarbonaceous deoxidizer which does not form a reaction product which is gaseous at room temperature upon combining with the oxygen oi the copper and sufilcient in amount to deoxidize the copper.

7. A method of making deoxidized copper comprising melting a plurality of succeeding charges of copper of approximately the same weight and composition under reducing conditions, exposing the succeeding melts to the air and agitating for the same definite'period of time to permit escape of gases, stirring carbonaceous material similar in composition to partly burned or calcined charcoal into the copper and for the same definite period of time for each melt, and deoxidizing the melts by adding noncarbonaceous deoxidizer which does not form a reaction product which is gaseous at room temperature upon combining with the oxygen of the copper.

8. The method of making deoxidized copper comprising melting a plurality of succeeding charges of copper of approximately the same weight and composition and exposing to reducing conditions for a suflicient time to substantially deoxidize the copper, exposing the succeeding melts to the air and stirring for the same definite period of time to permit escape of gases, stirring partly burned or calcined charcoal into the copper and for the same definite period of time for each melt, and adding to each melt suflicient metallic deoxidizer to deoxidize the copper.

9. A method .of making deoxidized copper comprising melting a plurality of succeeding charges of copper of approximately the .same weight and composition and bringing them to a substantially 'deoxidized condition, exposing the succeeding melts to the air and stirring for the coal into the copper for the same definite period' of time for each melt, and adding to each melt deoxidizer which does not forma reaction product which is gaseous at room temperature upon combining with the oxygen of the copper and sufilcient in amount to deoxidize the copper.

10. A method of making deoxidizedcopper J comprising -melting a plurality of succeeding charges of copper of approximately the same weight 'and'composition under reducing conditions, agitating the succeeding melts under oxidizing conditions for the same definite period of to each melt to deoxidiz the metal.

HERBERT c. Jamison. RICHARD B. MONTGOMERY. 

